This invention relates to an improved class of adhesion promoters for integrated circuit substrates and the like and to improved method of treating integrated circuit substrates such as aluminum; silicon, silicon dioxide, silicon nitride and the like and in particular the invention relates to methods employing organosilane compounds in order to improve the adhesion of a photoresist layer applied to a substrate.
Applicants are aware of U.S. Pat. Nos. 3,788,895; 3,827,908; 4,103,045 and 4,529,618. The disclosures of these patents are incorporated by reference herein.
In a photolithographic process, such as that used to make integrated circuit components and the like, a patterned photoresist is formed on a substrate and the pattern is etched into the substrate. One of the difficulties that occurs in this type of process is caused by unsatisfactory adhesion of the photoresist to the substrate. As the structures and patterns which are produced in the integrated circuit component become smaller, the problem caused by lack of adhesion becomes greater. Typically, the lack of adhesion results in intrusion of the developing solution (wet process) into the pattern during the wet etch step of the process. As a result, some of the pattern may be lifted off of the substrate and the resulting structure formed in the substrate does not have the desired circuitry. The desired circuitry may also be etched off in subsequent processing steps, such as developing.
In order to improve the adhesion of the photoresist layers, substrates such as silicon, silicon dioxide, silicon nitride and aluminum are treated with adhesion promoters or primers. Currently used primers or adhesion promoters of choice are silazanes and silanes, such as chlorosilanes, and aminoalkoxy silanes. This last group, the aminoalkoxysilanes, is especially effective with photoresist and, with silazanes, is accepted as standard by the industry. However, the aminoalkoxy silanes do have some draw backs, particularly when the structure to be produced in an integrated circuit component is at or below the one micron size. Conventional materials normally require a fairly high level of addition in order to achieve satisfactory adhesion. These materials are added from an aqueous solution containing from about 0.25 to 3% by weight or from organic solutions at higher levels. Applicants' adhesion promoters have greatly superior bond, particularly under adverse etching conditions and where the formed structure is of one micron or less in dimension.
Applicants have discovered a new class of adhesion promoting compounds which are effective at very low addition levels, for example, applicants' adhesion promoters may be added from solutions containing 0.1 weight percent or less. Moreover, applicants' adhesion promoters have greatly superior bond, particularly under adverse etching conditions and where the formed structure is of one micron or less in dimension.
Further, applicants have discovered an improved adhesion promoter containing an aqueous organic solvent mixture containing hydroxylic solvents. Such materials show increased stability in solution and improved adhesion in use.
Further, applicants have discovered that the adhesion promoting properties of adhesion promoting compounds may be improved significantly by adding a suitable catalyst, such as an acid or base, to the adhesion promoter. This improvement is observed both with applicants' novel adhesion promoting compounds and with conventional compounds.
Further, applicants have found that the adhesion promoting characteristic of silane adhesion promoting compounds may be further improved by the addition of an adhesion promoting polymer to the adhesion promoting composition.